At high enough leverage and normal trading conditions in forex(say 300:1+ which is beyond suicidal) you can lose all your money in seconds, which would never happen in stocks or options or futures (bearing a catstrophic fundamental announcement which is different)
I would say forex at normal leverage (100:1 and below) and options with 1 months or less to expiration, options are scarrier to trade than either options on stocks, options on futures, futures or stocks themselves.
I would put it this way, in terms of stress under regular conditions:
Options on stocks>Forex>Options on Futures>Futures>stocks
In terms of highest possible stress, forex kills them all.